refactor(crates): kernel/generation module split + DeerFlow optimizations + middleware + dead code cleanup

- Split zclaw-kernel/kernel.rs (1486 lines) into 9 domain modules
- Split zclaw-kernel/generation.rs (1080 lines) into 3 modules
- Add DeerFlow-inspired middleware: DanglingTool, SubagentLimit, ToolError, ToolOutputGuard
- Add PromptBuilder for structured system prompt assembly
- Add FactStore (zclaw-memory) for persistent fact extraction
- Add task builtin tool for agent task management
- Driver improvements: Anthropic/OpenAI extended thinking, Gemini safety settings
- Replace let _ = with proper log::warn! across SaaS handlers
- Remove unused dependency (url) from zclaw-hands

crates/zclaw-hands/Cargo.toml

@@ -20,6 +20,4 @@ thiserror = { workspace = true }
 tracing = { workspace = true }
 async-trait = { workspace = true }
 reqwest = { workspace = true }
-hmac = "0.12"
-sha1 = "0.10"
 base64 = { workspace = true }

crates/zclaw-hands/src/hands/quiz.rs

@@ -182,6 +182,9 @@ impl QuizGenerator for LlmQuizGenerator {
             temperature: Some(0.7),
             stop: Vec::new(),
             stream: false,
+            thinking_enabled: false,
+            reasoning_effort: None,
+            plan_mode: false,
         };
 
         let response = self.driver.complete(request).await.map_err(|e| {

crates/zclaw-hands/src/hands/slideshow.rs

@@ -96,7 +96,8 @@ pub struct SlideContent {
     pub background: Option<String>,
 }
 
-/// Content block types
+/// Presentation/slideshow rendering content block. Domain-specific for slide content.
+/// Distinct from zclaw_types::ContentBlock (LLM messages) and zclaw_protocols::ContentBlock (MCP).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case")]
 pub enum ContentBlock {